The invention provides a portable profile gage that senses the profile of a bore drilled through one or more layers of material and determines whether the bore is within required tolerance limits. The profile gage has great advantages over devices previously known in the art as it is hand held, easy to use, and provides a quick and accurate determination of whether a hole meets the required specifications.
The invention is particularly useful in operations where holes for rivets or other fasteners are drilled through one or more layers of material. Drilling holes through layers of different materials, and especially through stacks of composite materials and titanium, can be troublesome as the drill may chip or gouge one layer as it enters a second layer. Most fasteners are able to endure some flaws in the side surfaces of the drilled holes, but typical engineering specifications require that the overall sidewall surface of the hole be within 70-90% of the desired specification in order to ensure adequate support and resistance to shear forces on the shank of the fastener. Less than 70% contact between the fastener and the walls of the bore can result in lower joint fatigue endurance. If the hole is not within the desired tolerance range, corrective action must be taken before the fastener is inserted.
In automated drilling operations, it is difficult for the operator to determine accurately whether the inner surfaces of a bore are within acceptable tolerances simply by inspection. Some gaging device is necessary to provide an accurate profile. U.S. Pat. No. 4,290,204 to Possati describes a plug gage with "feelers" that move radially and contact the internal walls of a bore. U.S. Pat. No. 4,112,355 to Gibson et al. discloses a capacitance measuring device for detecting the quality and fit of tapered fastener holes. U.S. Pat. No. 3,757,569 to O'Brien et al. discloses a flaw or chip detector in which the gaging head is a roller element that moves over the internal surface of the bore. These devices are complicated and work in a different manner from the device of the present invention. The present invention provides a device that is easy and simple to operate and that quickly and accurately determines the profile of a hole and whether the hole is within prescribed tolerance limits.